It is our goal to set in motion a mechanism for finding a large number of hyperlipidemic persons living asymptomatically in the open population and exposing them to a variety of drug regimens for many years in efforts to define what treatment approach is most beneficial for which subgroups of these people. The results of therapy will be assessed mainly in terms of the effects on plasma lipid levels, but in addition, efforts will be made to increase our understanding of the pathophysiologic mechanisms involved in the different forms of hyperlipidemia: such studies will aim to provide a rational basis for therapy directed at specific pathogenetic factors. To this end, a number of basic studies of the metabolism of the lipids, especially of cholesterol and of lipoproteins, will be carried out at each of the three collaborating institutions to define these metabolic and/or genetic defects that lead to hyperlipidemia, using persons referred from a central screening clinic to satellite clinics in those institutions.